Chair having a clamping device for adjusting the inclination of the back and/or seat

ABSTRACT

It is possible to lock the inclination of the back of a seat by the locking device by means of a strip friction connection. The locking device is arranged as a modular unit with an axial motion by means of friction connection disk (13a) in bearings (10a) of the seating. A self-locking eccentric (17) bearing by its pivoting axis (16) on the tension rod (14) and with an extremely small rise of its eccentric curve is frontally engaged with the assembly of friction connection disks (13). Thus, part of the handling resistance of the eccentric is considerably reduced due to the small rise of its eccentric curve and on the other hand, due to a shortening, characteristic of the system, of the pivoting travel of the eccentric (17), said travel being still sufficiently short.

The invention relates to a chair as defined in the preamble of claim 1.

In a known chair of this type (DE-PS No. 2,927,377) the clamping deviceis axially supported at the seat or the seat carrier at which the leverfor shifting the friction lock is also mounted. The laminar frictionlock is controllable with the aid of the twin-arm lever design and thecooperation of tensionable spring washers. The friction lock is hereproduced and maintained by the spring washers. Such a clamping principleis therefore relatively expensive to produce. To release the frictionlock, the spring washers are compressed by means of the actuation leveruntil the friction lock is released. This requires a relatively largepath for the pivot movement of the lever.

A chair is also known which has a comparable clamping device (DE-OS No.2,335,586, FIG. 2a) where the laminar friction lock is establishedwithout the aid of spring means but with the aid of an eccentric. Inthis case, however, the clamping device, which is asymmetricallyarranged with respect to the plane of symmetry of the chair, is likewiseaxially supported at the seat or the seat carrier. Since such a clampingdevice requires that the eccentric be self-locking, the rise of theeccentric curve, when the eccentric engages at the frontal face of theclamping bolt, is of necessity relatively small. This small riserequires, on the one hand, less operating resistance, on the other hand,a relatively long pivot path for actuation of the eccentric.

In the known clamp mechanisms, the eccentric is always supported by astationary portion of the chair. Therefore, the axial movement requiredto establish or release the laminar friction lock is effectedexclusively by the axial thrust of the nonstationary (driving) part ofthe eccentric which must be designed for a correspondingly long thrust.

It is the object of the invention to modify a seat of theabove-mentioned species so that, with favorable conditions for economicmass production, the pivot path of the lever for operating the eccentricis shortened and thus manual control the clamping device is facilitated.

This is accomplished by the invention with the features defined in thecharacterizing portion of claim 1.

In such a configuration, the relative movement between the clamping boltand the adjacent friction lock discs produced by actation of theeccentric is converted into a simultaneous, but oppositely directedaxial movement of the friction lock discs and laminae disposed on oneside of the plane of symmetry a--a and the friction lock discs andlaminae disposed on the other side of this plane of symmetry. Thefriction lock discs and laminae on the side of the eccentric are pushedtoward the plane of symmetry. The friction lock discs and laminaedisposed on the other side of the plane of symmetry, however, are pulledtoward this plane of symmetry. This results in a shorter pivot path forthe eccentric whose pivot axis is fixed to the clamping bolts and whoseeccentric curves (eccentric discs) lie at the packet of friction lockdiscs. An approximately symmetrical construction of the clamping devicearranged symmetrically to the plane of symmetry is beneficial for massproduction.

The invention will be described below with reference to threeembodiments and the drawing.

It is shown in:

FIG. 1, a top view of the stationary seat of the chair with the seatshell removed and an adjustable-inclination support for the back rest;

FIG. 2, a bottom view of the seat,

FIG. 3, an enlarged sectional view along line III--III of FIG. 1 of theseat according to FIGS. 1, 2;

FIG. 3a, an enlarged sectional view along line IIIa--IIIa of FIG. 1 ofthe seat according to FIGS. 1, 2;

A further embodiment [is shown in] FIGS. 4-6, 6a.

FIG. 4, is a top view of the seat without set shell of the chair havingan adjustable-inclination support for the back rest.

FIG. 5 is a bottom view of the seat according to FIG. 4.

FIG. 6 is a sectional view along line VI--VI of FIG. 4 of the seat ofFIG. 4.

FIG. 6a is a sectional view along line VIa--VIa of FIG. 4 of the seat ofFIG. 4.

In both embodiments, the clamping device is accommodated in supportbearings 10a;10a' contained in vertical ribs arranged approximatelysymmetrically with respect to the plane of symmetry a--a of the chair.The clamping device includes packet (packet of laminae 12;12') oflaminae 12a;12a', which are articulated to the back rest and/or the seatsupport. The clamping device further includes a packet (friction lockdisc packet 13;13') of coaxial friction lock discs 13a;13a' whosefriction locking faces lie against the laminae. Also a clamping bolt14;14' which penetrates the laminae through long holes as well as thefriction lock discs and the ribs accommodating the clamping device.Finally, the clamping device includes a manually actuatable eccentric17,17' for controlling the clamping device by means of relativedisplacement (friction lock shift) between clamping bolts 14,14' on theone hand, and the packet of laminae and the friction lock disc packet13,13' on the other hand. It is significant that the clamping device, asa structural unit, is accommodated in support bearings 10a;10a' so as tobe axially movable and is retained in the axial position by the packetof laminae.

This axial mobility is assured by the given lateral play of laminae12a;12a'. Thus it is possible, with friction lock shifting, for frictionlock disc packet 13;13' (at which eccentric discs 17a;17a' engage) andclamping bolt 14;14' (in which the pivot axis 16;16' of the eccentric ismounted) to move simultaneously in the axial direction. As a result ofthis simultaneous movement, the pivot path of the actuating lever17b;17b' is cut approximately in half. The lever which is mounted in theclamping bolt by means of its pivot axis 16;16' and engages at the frontface of the friction lock disc packet is configured as a self-inhibitingeccentric 17;17'. The term "self-inhibiting eccentric" in the abovesense is understood to mean an eccentric whose eccentric curves engageat friction lock disc packet 13; 13' with such a flat slope angle that,due to the friction forces active between the eccentric curves and thefront face of the friction lock disc packet, the eccentric is unable torelease itself. The packet of friction lock discs 13;13' has such aconfiguration and arrangement that its plane of symmetry which isperpendicular to its axis approximately coincides with the plane ofsymmetry a--a of the chair. This results in an approximately symmetricalarrangement of the clamping device with respect to the plane of symmetrya-a. In this symmetrical position, the clamping device, in spite of itsaxially movable position, is retained approximately in the supportbearings by the laminae 12a;12a' which are articulated at one or bothends at a hinge axis. Finally, in both embodiments the pivot axis 16;16'of the eccentric 17;17' is configured as a cylindrical bearing boltwhich is perpendicular to the clamping bolt and has a bore through whichthe clamping bolt penetrates it. The bearing bolt is in communicationwith the clamping bolt 14;14' by means of an internal thread in itsbore. Eccentric 17;17' includes two eccentric discs 17a;17a' which aremounted at the free ends of the bearing bolt which serves as pivot axis16;16'. Support bearings 10a;10a' disposed on one side of the plane ofsymmetry a--a are each penetrated by a single friction lock disc13a;13a'. Compared to friction lock discs 13b;13b', which are disposedin the region between laminae 12a;12a', friction lock discs 13a;13a'have much larger dimensions in the axial direction in the region ofsupport bearings 10a;10a'. All support bearings 10a;10a' are part of asingle cast piece which, in the embodiment according to FIG. 1-3, 3a isan injection molded plastic member and, in the embodiment according toFIGS. 4-6, 6a, a cast aluminum member.

For the embodiment of FIGS. 1-3, 3a the following applies: the seat isformed of a supporting shell 10 and an approximately congruent seatshell (not illustrated) which is mounted on this supporting shell. Theseat shell rests on the edge of supporting shell 10 and is additionallysupported and centered on the supporting column 10f of supporting shell10. In the interior of supporting shell 10, there are numerousreinforcement ribs 10c which are symmetrical to the plane of symmetrya--a. Sleeves are shaped to two vertical reinforcement ribs extendingparallel to this plane of symmetry a--a so as to form the supportbearing 10a for the clamping device. Fastening faces 10d accommodate thesupports for the arm rests. Openings 10e serve to guide the actuationmember for the height adjustment of the seat. The upwardly orientedrecess 10g in the bottom of supporting shell 10 provides a free spacefor pivoting eccentric 17. The approximately vertical rear edge 10idefines an approximately block-shaped housing member 10h which is openat the rear. In this part of the housing, a support 11 formed by ahollow, ejection molded plastic member, is defined by means of pivotaxis 30 and is pivotally mounted. The ejection molded plastic memberends in an approximately perpendicular sleeve 11a which is suitable toreceive the support arm for the back rest. A reset spring 31 imparts atendency to the back rest of inclining it toward the back of the user ofthe chair and the user imparts the desired inclination to the back restby correspondingly leaning against it. The hinge axis 18 is spaced frompivot axis 30 and is mounted parallel to pivot axis 30 in carrier 11.The seat and thus also seat shell 10 are placed rigidly onto the centralsupporting spindle of the chair. For this purpose, a sleeve 10b isshaped into seat shell 10 which itself is lined by a metal bush 25. Seenfrom a function point of view, the support shell 10 is thussimultaneously the support for the seat and accommodates the seat in theform of the seat shell.

In the embodiment of FIGS. 4-6, 6a, the seat is defined by a supportingframe 10' and a seat shell (not illustrated). The latter is supported onsupport faces 10d' of the support frame and is connected therewith bymeans of fastening members 10f'. Frame sections of supporting frame 10'extending parallel to the plane of symmetry a--a are each provided withtwo reinforcement ribs 10c';10c", which likewise extend parallel to theplane of symmetry a--a. Support bearings 10a' for the clamping deviceare formed by coaxial bores in these reinforcing ribs 10c';10c". Thethin reinforcing ribs 10c" (FIGS. 4, 6) extend close to the plane ofsymmetry a--a. The hinge axis 18' is accommodated in lugs 20a of support20 for the back rest which is articulated, with the aid of a bearingsleeve 22, at an axis 31 of supporting frame 10'. With the aid of itspivot bearings 10k, supporting frame 10' is pivotally connected withseat support 23. Pivot bearings 10k are accommodated in bearing sleeves23a which are shaped to seat supported 23. Seat support 23 isaccommodated, via central bore 23b, by the supporting spindle of thefoot rest. The inclination of the seat can be set by the user of thechair by appropriately displacing the center of gravity against theforce of a reset spring 37 which is supported at one end, at 32 onsupporting frame 10' and at the other end, at 33, at the not pivotalseat support 23 at 33. As can be seen in FIG. 4, the bores in ribs 10c'and 10c" are penetrated at each side of the plane of symmetry by asingle friction lock disc 13a'. Laminae 12a of the packet of laminae 12'are articulated, one the one hand, at a hinge axis 34 of seat support 23and, on the other hand, at hinge axis 18' of the back rest. The spatialassociation of hinge axes 18', 34 and clamping bolt 14' is such that achange in inclination by means of the clamping device results in adisplacement ratio between seat 23 and back rest of about 1:2.

In both embodiments, the clamping bolt is supported at friction lockdisc packet 13,13' by means of a screw nut 15;15'.

Eccentric and clamping bolt are secured against rotation on supportingframe 10' by means of ribs 36 (FIG. 5).

I claim:
 1. Chair, particularly a roatable office chair, having a footrest which includes a central supporting spindle, seat means (10, 23)carried by the support spindle and having vertical ribs (10c;10c';10c")formed to define support bearings (10a;10a') which are located at leastapproximately symmetrically to the plane of symmetry of the chair, aback rest carried by the seat means, and a clamping device supported inthe bearings and connected to at least one of the seat means and backrest for adjusting the inclination of at least one of the seat means andback rest by laminar friction,said clamping device being composed of: apacket (12,12') of laminae (12a;12a') which are provided with elongatedholes and are articulated to at least one of the seat means and backrest; a friction lock disc packet (13;13') of annular, coaxial frictionlock discs (13a;13b;13a';13b') having friction locking faces which lieagainst the laminae (12a;12a'); a clamping bolt (14;14') which passesthrough the laminae and discs; and a manually actuable lever operativelyassociated with the clamping bolt for effecting relative displacementbetween the clamp bolt and the laminae and discs in order to control theclamping of the laminae between the discs; characterized in that; saidfriction lock discs are movably mounted in said support bearings, sothat said clamping device is movable in the direction of the axis ofsaid clamping bolt; the plane of symmetry of the chair passes throghsaid packet of laminae and said friction lock disc packet; and saidlever constitutes a self-inhibiting eccentric having a pivot axis fixedto said clamping bolt and bears against one end of said friction lockdisc packet such that pivotal movement of said lever about its pivotaxis causes axial displacement of said clamping bolt and causes theparts of said packet of laminae and friction lock disc packet which arerespectively opposite sides of the plane of symmetry of the chair tomove in respectively opposite directions.
 2. Chair according to claim 1,characterized in that the friction lock disc packet (13;13') is disposedapproximately symmetrically to the vertical plane of symmetry (a--a) ofthe chair.
 3. Chair according to claim 13, characterized in that saidlever includes a cylindrical bearing bolt which is perpendicular to theclamping bolt (14;14'), defines the pivot axis of said lever and has aninternaly threaded bore in which said clamping bolt is fixed.
 4. Chairaccording to claim 1, characterized in that the eccentric (17;17')includes two eccentric discs (17a;17a') whose eccentric curves engage atthe frontal face of the adjacent friction lock disc (13; 13a') andthrough which penetrate the free ends of the pivot axis (16;16'). 5.Chair according to claim 1, characterized in that the support bearings(10a;10a') disposed on either side of the plane of symmetry (a--a) areeach penetrated by a single friction lock disc (13a;13a').
 6. Chairaccording to claim 1, characterized in that all support bearings(10a;10a') are components of a single cast piece.
 7. Chair according toclaim 6, characterized in that the cast member is an injection moldedplastic member which supports a seat shell (not shown) that has the samebasic outline as the seat (FIGS. 1-3, 3a).
 8. Chair according to claim7, characterized in that the support bearings (10a) are formed bysleeves which are shaped to vertical ribs of the injection moded plasticmember.
 9. Chair according to claim 7, characterized in that said chairfurther comprises a hinge having an axis and connecting said seat backto said seat means and the laminae (12a) of the clamping device, whichserves exclusively for adjusting the inclination of the seat back arepenetrated, at one end, by the hinge axis (18).
 10. Chair according toclaim 6, characterized in that said seat means comprise a seat supportrigidly held by the support spindle and an adjustable-inclinationsupport frame pivotally supported by said seat support, and said castpiece is produced by metal ejection molding, is made of aluminum, andforms said adjustableinclination support frame.
 11. Chair according toclaim 10, characterized in that the support bearings (10a') are formedby bores in four vertical ribs of the cast member which are arrangedsymmetrically to the plane of symmetry (a--a) and each pair of bores oneach side of the plane of symmetry (a--a) is penetrated by a singlefriction lock disc (13a').
 12. Chair according to claim 10,characterized in that said chair further comprises a hinge having anaxis and connecting said seat back to said support frame, said laminae(12a') are articulated, on the one hand, to the seat support (23) and,on the other hand, to the hinge axis (18') of the back rest in such amanner that, if the inclination is changed by means of the clampingdevice, a displacement ratio between the seat support (23) and back restof about one to two results.